A high-power short pulse (a few picoseconds or less) solid-state MOPA system for material processing applications typically includes a mode-locked master oscillator which provides seed-pulses in a train at a pulse repetition rate (PRF) of several megahertz (MHz). A pulse-picker is provided for selecting single pulses or bursts of pulses from the seed-pulse train for further amplification at a lower PRF, for example, hundreds of kilohertz (kHz). The selected pulses are amplified by one or more solid-state amplifier stages. A fast process shutter, usually an electro-optic (EO) modulator is used to select from the amplified pulses, those that are delivered to material being processed.
The fast process shutter adds significant cost and complexity to such a MOPA system. There is a need for a method and apparatus for operating such a MOPA system without a fast process shutter. This method and apparatus must avoid over-amplification of the first pulse in a train to be delivered to the material being processed.